Copper is a well-known material for wiring of microelectronic devices. Diffusion barriers prevent diffusion of copper, oxygen (O2), and water (H2O), for example, into silica surfaces of the microelectronic devices. In a recent industry trend, Manganese silicate (MnSiOx) is a newly introduced self-forming barrier (SFB) to replace conventional diffusion barriers.
A known approach of SFB involves a self-forming barrier process by chemical vapor deposition (CVD) of manganese (Mn), wherein the Mn diffuses into a silicon-based (Si-based) insulating layer to form a MnSiOx barrier on the sidewalls of a via, as illustrated in FIGS. 1A through 1F. In particular, a metal line 101, e.g., of copper, is formed in a substrate 103. Next, a capping layer 121, e.g., silicon nitride (SiN), is formed on the substrate 103, as depicted in FIG. 1B. Then, a Si-based insulating layer 123 is formed on the capping layer 121. Adverting to FIG. 1C, a via is formed in the Si-based insulating layer 123 down to the metal line 101. Thereafter, a Mn layer 141 is formed on the sidewalls of the Si-based insulating layer 123 and metal line 101 using CVD, as illustrated in FIG. 1D. Adverting to FIG. 1E, as a result of a sufficiently high deposition temperature or thermal annealing, the Mn barrier 141 reacts with the Si-based insulating layer 123 to form a MnSiOx barrier 143 on the sidewalls of the via. However, the Mn layer 141 on the bottom of the via does not similarly react with the metal line 101. Thereafter, the via is filled with a metal 161, e.g., copper, as illustrated in FIG. 1F. The absence of a MnSiOx barrier on the bottom of the via causes a degradation of device reliability due, for example, to elecromigration.
A need therefore exists for methodology enabling formation of a self-forming barrier that protects both the sidewalls and bottom of a via against unwanted diffusion and/or electromigration, and the resulting device.